Cupola structure

ABSTRACT

Mounted adjacent the closed top of a cupola stack is a hopper which rains a torrent of discrete heat-exchange particles such as sand downwardly through the upward flowing hot gases in the stack. Deflectors within the stack deflect the torrent toward a discharge opening in the side of the stack above the melt zone. Accumulated particles adjacent the discharge opening seal the gases against escape therethrough. An outlet from an expansion chamber adjacent the top of the stack passes the cooled gases to a conventional filter which removes the smoke burden from the gases.

0 United States Patent [191 [in 3,731,910

Butler May 8, 1973 [54] CUPOLA STRUCTURE [76] Inventor: Thomas J.Butler, 7625 E. Morrow Primary Ca mby Circle Dearbom, Mich 48126Attorney-Barnes, Kisselle, Raisch & Choate [22] Filed: May 17, 1971ABSTRACT [21] Appl' 144,024 Mounted adjacent the closed top of a cupolastack is a V hopper which rains a torrent of discrete heat-exchange [52]US. Cl. 266/15, 266/31, 55/262, 55/267, 432/67 particles such as sanddownwardly through the upward [51] Int. Cl ..F27b 1/18 flowing hot gasesin the stack. Deflectors within the [58] Field of Search ..263/29, 50;266/15, stack deflect the torrent toward a discharge opening in 266/17the side of the stack above the melt zone. Accumulated particlesadjacent the discharge opening seal the References Cited gases againstescape therethrough. An outlet from an expansion chamber adjacent thetop of the stack UNITED STATES PATENTS passes the cooled gases to aconventional filter which 3,645,515 2/1972 Kemmetmueller ..263/32removes the smoke burden from the gases. 1,884,088 l0/l932 Miller....266/l7 X 3,507,482 4/1970 Kraszewski et a1. ..263/32 R 17 Claims, 3Drawing Figures PATENTEDIW 81915 3,731,910

' INVENTOR. THOMAS J. BUTLER ATTOPNEYC;

CUPOLA STRUCTURE This invention relates to a cupola for producing moltenmetal such as iron. More particularly, the invention involves animprovement of the cupola structure which facilitates cooling the gasestherein to such an extent that the gases can be passed directly from thecupola stack to a conventional filter for removing the smoke burdenwithout damage to the filter.

Gases issue from a typical cupola at about 2,000 F. at a rate of manythousands of cubic feet per minute and are heavily laden with smoke. Bysmoke is meant particulate, unburned products of combustion such as coalor coke fines, ash, metal oxide fines, and the like. Because of thiscombination of high heat, high volume, and heavy smoke burden, noapparatus or system devised before the present invention has beencapable on a reasonably economical basis of effectively removing thesmoke from gases issuing from a cupola.

A particularly knotty problem is that gases issuing from a cupola are sohot that they cannot be handled by conventional filters. A conventionalapproach to this problem has been to subject the gases to a spray orstream of cooling and cleansing water. This approach has beenunsatisfactory because it generates steam which increases the volume ofthe gases and compounds the difficulty of their handling; the waterleaves a residue of smoke burden which must be removed by other means;the water does not cool the gases sufficiently for handling byconventional filtering devices; and water-cooling systems are veryexpensive to build, operate, and maintain. Typically, the initial costof such a system ranges from about $200,000 to about $600,000, its waterconsumption and power requirements are very high, and continualmaintenance is required.

The object of the present invention is to provide a cupola structureimproved so that the smoke-laden gases can be cooled within the cupolastack itself to such an extent that the gases issue from the stack at atemperature and volume within the handling capabilities of conventionalfiltering or collecting equipment, the structure being relatively simpleto build, operate and maintain so that it is economically available foruse by industrial concerns of moderate financial means.

In general, the invention is carried out by closing the upper end of thestack and providing adjacent its upper end a hopper which rains atorrent of discrete, heat-absorptive particles such as sand or metalshot downwardly through the stack. The upwardly flowing gases are cooledby the particles and arrive at the top of the stack at about 200 F. andcommcnsurately diminished volume. The gases in this condition can befiltered by conventional filtering or collecting devices. Deflectors areprovided within the stack to deflect the torrent of particles toward adischarge opening in a side portion of the stack above the melt zone.The deflectors shield the melt zone from penetration by significantquantities of the heat-absorptive particles.

One form of the invention is illustrated in the accompanying drawings.

FIG. 1 is a partly diagrammatic representation of a cupola embodying thepresent invention.

FIG. 2 is an enlarged fragmentary diagrammatic view of an aperturedhopper bottom and gate plate associated therewith.

FIG. 3 is a generally elevational view in the direction of arrow 3 ofFIG. 1, parts being broken away and shown in phantom to illustratestructural details.

Shown in FIG. 1 is a cupola 10 according to the present invention havinga charge door 12 through which a charge is introduced into melt zone 13by such means as a charger 14. Typically, where the cupola is used inproducing molten iron, the charge includes coke, iron, or steel, andslag-producing material such as limestone. Combustion air is introducedinto the cupola by means ofa manifold 16 and tuyers 18. The molten metalis drawn off by a trough or launder 20. As is conventional, cupola 10has a stack 22 which extends upwardly of charge door 14.

In accordance with the invention, the upper end portion 24 of stack 22has an enlarged diameter to define an expansion chamber 26. The top ofthe expansion chamber is closed by a closure 28. A hopper or container30 is mounted adjacent the upper end of the stack; and in the structureillustrated, hopper 30 is suspended from closure 28 within expansionchamber 26.

A chute 32 communicates into the interior of hopper 30 through anopening 34. A mass 36 of heat-absorptive particles is introduced intohopper 30 through chute 32 and opening 34. The mass of particles restsupon and substantially covers the bottom 38 of the hopper (FIG. 2).Bottom 38 is provided preferably throughout its area with a number ofdownward openings 40.

Beneath hopper bottom 38 is a gate plate 42 which is movably mounted sothat a number of openings 44 therein can be shifted to and from registrywith openings 40. Gate 42 is moved by suitable means such as a controlarm 46 (FIG. 1). Openings 40, 44 are preferably distributed over a majorportion of the diameter of stack 22. When openings 40 and 44 are inpartial or full registry, a number of streams of particles from mass 36rain in a free-falling torrent downwardly through stack 22, the volumeof which is adjustable by moving gate 42.

Mounted within stack 22 are an upper deflector 48 and a lower deflector50 both of which are sloped to deflect the rain of heat-absorptiveparticles toward a discharge opening 52 in a side portion of stack 22above melt zone 13. Lower deflector 50 has curved edge portions 54secured to the stack interior so that the lower deflector and adjacentportions of the stack interior define a receptacle 56 within which theheatabsorptive particles accumulate for discharge through opening 52.

Upper deflector 48 has edge portions 58 secured to interior portions ofstack 22 which are generally on the opposite side of the stack from edgeportions 54 of the lower deflector. Deflectors 48 and 50 have free edges60 and 62 which extend generally across the diameter of stack 22 andwhich are vertically displaced from each other to define a passageway 64facilitating the flow of hot gases upwardly past the deflectors as shownby the arrows in FIG. 1. Passageway 64 has an effective area generallyapproximating that of the interior of stack 22.

Deflector 4% overlaps deflector 50 in a horizontal direction to preventthe falling heat-absorptive particles from penetrating to melt zone 13in significant quantity. It makes little or no difference to operationof the cupola if small quantities of the particles do penetrate to themelt zone.

Expansion chamber 26 has an outlet 66 communicating into a pipe 68 whichconducts cooled gases to a filter or collector 70 which is illustratedas being a conventional, commercially available, cloth-bag typecollector. The collector is provided with an exhaust blower 72 operatedby an electric motor 74.

Means are provided for cooling the heated particles issuing fromdischarge outlet 52 and for returning the cooled particles to hopper 30.In the illustrated system, these means comprise a stack 76 having anenlarged upper portion 78 forming an expansion chamber and having anopen upper end 80. A hopper 82 is mounted by suitable means in expansionchamber 78, and this hopper may be identical in construction to hopper30 having a bottom 38 and associated gate plate 42 provided respectivelywith openings 40, 44 distributed over their area for raining a torrentof the heated particles downwardly through stack 76. A chute 84 conductsthe heated particles from discharge opening 52 into hopper 82 where theycollect in a mass 86 on the bottom of hopper 82. A blower 88 blows adraft of cooling air upwardly through stack 76 and expansion chamber 78for discharge upwardly out of open end 80.

Stack 76 has a bottom chute 90 which discharges the cooled particlesinto the inlet 92 of a bucket-type elevator 94 which returns theparticles to chute 32 and hopper 30.

Any discrete, particulate, heat-absorptive material can be used which issufficiently dense so that it will pass downwardly through stack 22without being unduly impeded by the counter current of hot gasestherein. Metal shot or particles, for example, could be used providedthat the metal itself has a melting point higher than the temperature ofthe gases issuing from melt zone 13. However, sand is preferred becauseof its very low cost. A typical example of a sand suitable for use inthe cupola is commercial grade foundry mold sand or bank sand having agrain size of about one-half millimeter.

in operation, it may be assumed that cupola has been charged and is inoperation to produce a melt. Hot smoke-laden gases pass upwardly frommelt zone 13 through passageway 64 and upwardly through stack 22 toexpansion chamber 26 and then out of the cupola at outlet 66. With gateplate 42 properly adjusted to provide a desired extent and rate of heatexchange, a torrent of sand rains downwardly through stack 22 in asubstantially free gravitational fall unimpeded except by the buoyanteffect thereon of the upwardly flowing gases and the effect ofdeflectors 48, 50.

Since openings 40 and 44 in hopper bottom 38 and gate plate 42respectively are generally distributed over the diameter of stack 22,the sand enters the stack in a plurality of generally uniformlydistributed streams which insures that gases in all parts of thesectional area of the stack contact the particles. Moreover, within thestack, the streams are broken up or dissipated by the upwardly flowinggases which results in a thorough distribution of the sand particleswithin the stack and a consequent high rate of heat exchange between thegases and sand.

The same particles have a very large total surface area so that theyquickly absorb heat from the gases. When the gases enter expansionchamber 26, they have been cooled to a temperature at which they willnot damage collector 70. Upon passing through the collector,substantially all of the smoke particles carried by the gases areremoved and the gases are discharged as clean air to the atmospherethrough blower 72.

Expansion chamber 26 diminishes the velocity of the gases so that theydrop whatever sand particles they may have carried upwardly into theexpansion chamber, and such particles are not blown through outlet 66 tocollector 70.

The mass of sand 36 in hopper 30 seals openings 40, 44 to prevent theescape of smoke-laden gases from the expansion chamber directly to theatmosphere. Deflectors 48 and cooperate to deflect the falling sand intoreceptacle 56 where the sand accumulates and forms a seal which preventsthe escape of the gases through discharge opening 52. Movement of thesand over the surfaces of the deflectors tends to cool the deflectorsand helps to prevent their overheating by the hot gases.

Deflectors 48 and 50 tend to form restrictions to the flow of gases instack 22. ln general, however, these restrictions are compensated for bythe draft resulting from rapid shrinkage of the gases above therestrictions and the suction of exhaust blower 72. If necessary, stack22 could be provided with radial enlargements adjacent the deflectors todiminish or eliminate the restrictions.

A typical cupola 10 produces molten metal at a rate of about 12 tons perhour. The gases from melt zone 13 pass upwardly through the lowerportions of stack 22 at a temperature of about 2,000 F. and at a rate offlow of about 25,000 cfm. The inner diameter of such a cupola istypically about 66 inches. In accordance with the present invention, asuitable height for stack 22 is about 16 feet measured from the top edge62 of deflector 50 to the bottom 96 of expansion chamber 26.Accordingly, the sand, in its free gravitational fall, takes about 1second to fall from openings 44 to receptacle 56. However, the upwardlyflowing gases in the stack impede the fall of the sand to a certainextent and any given volume of gases and sand are in heat exchangecontact for more than one second within stack 22.

In the l2-ton cupola under consideration, sand is rained downwardlythrough stack 22 at a rate of about 40 tons per hour. The mass 36 ofsand in hopper 30 need not exceed that necessary to insure a continuedrain through stack 22 during minor down time of elevator conveyor 94. Asa practical matter, 5 to 6 tons is adequate to meet this requirement.

As the gases pass upwardly and are cooled, they shrink in volumecommensurately. When they reach expansion chamber 26, the gases havebeen cooled to about 200 F., and their rate of flow has diminished toabout 9,000 cfm because of their smaller volume. At this temperature,the gases cause no damage to collector 70. The gases enter outlet 66traveling at a lineal velocity of about 500 feet per minute which is lowenough so that, except for fines which may be contained in the sand, thesand is not blown into pipe 68.

The temperature of the sand is raised from ambient to about l,400 F. inpassing from hopper 30 through stack 22 to receptacle 56, and the sandenters hopper 82 at somewhat less than that temperature. To cool thesand to about ambient temperature, stack 76 has an internal diameter ofabout feet, a height of about 16 feet between the outlet of blower 88and the bottom of hopper 82, and blower 88 blows cooling air into stack76 at about 58,000 cfm. The sand is returned to hopper 30 by elevatorconveyor 94 at ambient temperature.

Expansion chamber 78 reduces the lineal velocity of the cooling air tobelow 400 feet per minute so that no sand is blown out of outlet 80 andthe air need not be passed through a filter or collector. Clean airissues from outlet 80. This air is in heated condition and can be usedfor space heating or other purposes or can be discharged to theatmosphere.

The assembly of expansion chamber 26, its cover 28, and hopper 30together with its mass 36 of sand is light enough so that it can bemounted on top of a conventional stack 22.

The cost of cupola modifications according to this invention installedand in operation, together with the accessory equipment illustrated, isabout $40,000. Moreover, if a relatively large storage hopper or bin isavailable for heated sand issuing through chute 84, the sand could beallowed to cool simply by radiation, thereby eliminating entirely thecooling apparatus 76-90 and effecting a further savings of severalthousand dollars. in comparison, the initial cost of a conventionalapparatus for depolluting the gases from a l2-ton per hour cupola isabout $200,000.

The operating cost of a cupola 10 according to this invention and itsaccessory equipment is very low, requiring only two or less relativelylow power blowers 72, 88 and a relatively inexpensive elevator conveyor94. The sand is an extremely cheap heat exchange medium, and it isrecycled time after time rather than being expended. The cupola is notsubject to clogging by smoke particles, and the cupola can be operatedcontinuously without the necessity of periodic stoppages to permitcooling of the functional parts of the cupola or its accessoryequipment.

I claim:

1. In a cupola having a melt zone adjacent its lower portion forreceiving a charge and a stack for hot gases above said melt zone,improved structure which comprises,

said stack having a closed upper end,

a container mounted adjacent said upper end and having a body of soliddiscrete particles contained therein,

means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack,

said stack having an opening in its side above said melt zon e,

deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack,

said deflector means also forming shield means effective to shield saidmelt zone against entry thereinto of said particles in significantquantity,

said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end,

said stack having an outlet for the gases adjacent said upper end,

and a filter connected with said outlet effective to remove particulatematter carried by the gases issuing through said outlet.

2. In a cupola having a melt zone adjacent its lower portion forreceiving a charge and a stack for hot gases above said melt zone,improved structure which comprises,

said stack having a closed upper end,

a container mounted adjacent said upper end and having a body of soliddiscrete particles contained therein,

means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack,

said stack having an opening in its side above said melt zone,

deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack,

said deflector means also forming shield means effective to shield saidmelt zone against entry thereinto of said particles in significantquantity,

said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end,

said stack having an outlet for the gases adjacent said upper end,

and a filter connected with said outlet effective to remove particulatematter carried by the gases issuing through said outlet,

said deflector elements comprising a lower element and an upper element,

said lower element cooperating with the interior of said stack to form areceptacle for collecting said particles in a mass,

said opening being adjacent the bottom of said receptacle to facilitatedischarge of the massed particles therethrough,

said mass forming a seal which contains the gases from escape throughsaid opening.

3. The structure defined in claim 2 wherein said upper element iseffective to deflect portions of said torrent toward said receptacle.

4. The structure defined in claim 3 wherein said elements are disposedadjacent diametrically opposite portions of the stack interior, and eachextends more than half way across the diameter of said stack so thatsaid elements overlap in a horizontal direction to form said shieldmeans.

5. The structure defined in claim 4 wherein the overlapped portions ofsaid elements terminate in edges which are spaced apart in a verticaldirection to define said passageway.

6. In a cupola having a melt zone adjacent its lower portion forreceiving a charge and a stack for hot gases above said melt zone,improved structure which comprises,

said stack having a closed upper end,

a container mounted adjacent said upper end and having a body of soliddiscrete particles contained therein,

means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack,

said stack having an opening in its side above said melt zone,

deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack,

said deflector means also forming shield means effective to shield saidmelt zone against entry thereinto of said particles in significantquantity,

said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end,

said stack having an outlet for the gases adjacent said upper end,

and a filter connected with said outlet effective to remove particulatematter carried by the gases issuing through said outlet,

said deflector elements including an upper element and a lower element,

said upper element extending across a portion of the diameter of saidstack and being sloped to deflect the particles impinging thereon towardthe side of said stack having said opening,

said lower element extending across at least the remaining portion ofthe diameter of said stack for impingement by particles both deflectedby and passing freely of said upper element,

said lower element being sloped to deflect particles impinging thereontoward said opening.

7. The structure defined in claim 6 wherein there is vertical spacingbetween said elements which forms said passageway.

8. The structure defined in claim 7 wherein there is a horizontaloverlap of said elements which provides said shield means.

9. In a cupola having a melt zone adjacent its lower portion forreceiving a charge and a stack for hot gases above said melt zone,improved structure which comprises,

said stack having a closed upper end,

a container mounted adjacent said upper end and having a body of soliddiscrete particles contained therein,

means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack,

said stack having an opening in its side above said melt zone,

deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack,

said deflector means also forming shield means effective to shield saidmelt zone against entry thereinto of said particles in significantquantity,

said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end,

said stack having an outlet for the gases adjacent said upper end,

and a filter connected with said outlet effective to remove particulatematter carried by the gases issuing through said outlet,

said stack having an enlarged diameter adjacent said upper end formingan expansion chamber for diminishing the rate of flow of said gasesprior to passing into said outlet.

10. The structure defined in claim 9 wherein said container is mountedwithin said expansion chamber.

11. The structure defined in claim 10 wherein the top of said expansionchamber has a closure, said container being suspended from said closurewithin said expansion chamber.

12. The structure defined in claim 5 wherein said stack has an enlargeddiameter adjacent said upper end to form an expansion chamber fordiminishing the rate of flow of said gases prior to passing into saidoutlet.

13. The structure defined in claim 12 wherein said upper end is closedby a closure, said container being mounted on said closure.

14. In a cupola having a melt zone adjacent its lower portion forreceiving a charge and a stack for hot gases above said melt zone,improved structure which comprises,

said stack having a closed upper end,

a container mounted adjacent said upper end and having a body of soliddiscrete particles contained therein,

means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack,

said stack having an opening in its side above said melt zone,

deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack,

said deflector means also forming shield means effective to shield saidmelt zone against entry the-l'einto of said particles in significantquantity,

said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end,

said stack having an outlet for the gases adjacent said upper end,

and a filter connected with said outlet effective to remove particulatematter carried by the gases issuing through said outlet,

cooling means effective to cool particles discharged through saidopening, and conveyor means operable to convey the cooled particles tosaid container.

15. In a furnace having a melt zone for metals and a stack for receivinghot gases from said melt zone, improved structure which comprises,

a closure adjacent the upper end of said stack,

a container mounted adjacent said upper end and having a body of soliddiscrete particles contained therein,

means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent disdiminishing the rate of flow of said gases prior totributed across a major portion of the diameter of passing into saidoutlet. said stack, 16. The structure defined in claim 15 and includingsaid stack having an opening below said torrent for egress of saidparticles,

conveyor means operable to return to said container particles which haveissued from said opening whereby to recycle said particles,

said stack having an outlet for gases adjacent said upper end, 10

said stack having an enlarged portion adjacent said upper end whichforms an expansion chamber for in addition means effective for coolingsaid particles between issuance thereof from said opening and recyclingthereof.

17. The structure defined in claim and including in addition a filterconnected with said outlet effective to remove particulate mattercarried by the bases issuing through said outlet.

1. In a cupola having a melt zone adjacent its lower portion forreceiving a charge and a stack for hot gases above said melt zone,improved structure which comprises, said stack having a closed upperend, a container mounted adjacent said upper end and having a body ofsolid discrete particles contained therein, means operable to introduceparticles from said container into said stack adjacent said upper end inthe form of a substantially freely falling torrent distributed across amajor portion of the diameter of said stack, said stack having anopening in its side above said melt zone, deflector means in said stackeffective to deflect said torrent of particles toward said opening fordischarge from said stack, said deflector means also forming shieldmeans effective to shield said melt zone against entry thereinto of saidparticles in significant quantity, said deflector means having elementsspaced apart to define a passageway which facilitates flow of hot gasesfrom said melt zone through said torrent toward said upper end, saidstack having an outlet for the gases adjacent said upper end, and afilter connected with said outlet effective to remove particulate mattercarried by the gases issuing through said outlet.
 2. In a cupola havinga melt zone adjacent its lower portion for receiving a charge and astack for hot gases above said melt zone, improved structure whichcomprises, said stack having a closed upper end, a container mountedadjacent said upper end and having a body of solid discrete particlescontained therein, means operable to introduce particles from saidcontainer into said stack adjacent said upper end in the form of asubstantially freely falling torrent distributed across a major portionof the diameter of said stack, said stack having an opening in its sideabove said melt zone, deflector means in said stack effective to deflectsaid torrent of particles toward said opening for discharge from saidstack, said deflector means also forming shield means effective toshield said melt zone against entry thereinto of said particles insignificant quantity, said deflector means having elements spaced apartto define a passageway which facilitates flow of hot gases from saidmelt zone through said torrent toward said upper end, said stack havingan outlet for the gases adjacent said upper end, and a filter connectedwith said outlet effective to remove particulate matter carried by thegases issuing through said outlet, said deflector elements comprising alower element and an upper element, said lower element cooperating withthe interior of said stack to form a receptacle for collecting saidparticles in a mass, said opening being adjacent the bottom of saidreceptacle to facilitate discharge of the massed particles therethrough,said mass forming a seal which contains the gases from escape throughsaid opening.
 3. The structure defined in claim 2 wherein said upperelement is effective to deflect portions of said torrent toward saidreceptacle.
 4. The structure defined in claim 3 wherein said elementsare disposed adjacent diametrically opposite portions of the stackinterior, and each extends more than half way across the diameter ofsaid stack so that said elements overlap in a horizontal direction toform said shield means.
 5. The structure defined in claim 4 wherein theoverlapped portions of said elements tErminate in edges which are spacedapart in a vertical direction to define said passageway.
 6. In a cupolahaving a melt zone adjacent its lower portion for receiving a charge anda stack for hot gases above said melt zone, improved structure whichcomprises, said stack having a closed upper end, a container mountedadjacent said upper end and having a body of solid discrete particlescontained therein, means operable to introduce particles from saidcontainer into said stack adjacent said upper end in the form of asubstantially freely falling torrent distributed across a major portionof the diameter of said stack, said stack having an opening in its sideabove said melt zone, deflector means in said stack effective to deflectsaid torrent of particles toward said opening for discharge from saidstack, said deflector means also forming shield means effective toshield said melt zone against entry thereinto of said particles insignificant quantity, said deflector means having elements spaced apartto define a passageway which facilitates flow of hot gases from saidmelt zone through said torrent toward said upper end, said stack havingan outlet for the gases adjacent said upper end, and a filter connectedwith said outlet effective to remove particulate matter carried by thegases issuing through said outlet, said deflector elements including anupper element and a lower element, said upper element extending across aportion of the diameter of said stack and being sloped to deflect theparticles impinging thereon toward the side of said stack having saidopening, said lower element extending across at least the remainingportion of the diameter of said stack for impingement by particles bothdeflected by and passing freely of said upper element, said lowerelement being sloped to deflect particles impinging thereon toward saidopening.
 7. The structure defined in claim 6 wherein there is verticalspacing between said elements which forms said passageway.
 8. Thestructure defined in claim 7 wherein there is a horizontal overlap ofsaid elements which provides said shield means.
 9. In a cupola having amelt zone adjacent its lower portion for receiving a charge and a stackfor hot gases above said melt zone, improved structure which comprises,said stack having a closed upper end, a container mounted adjacent saidupper end and having a body of solid discrete particles containedtherein, means operable to introduce particles from said container intosaid stack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack, said stack having an opening in its side above said meltzone, deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack, saiddeflector means also forming shield means effective to shield said meltzone against entry thereinto of said particles in significant quantity,said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end, said stack having an outlet for the gasesadjacent said upper end, and a filter connected with said outleteffective to remove particulate matter carried by the gases issuingthrough said outlet, said stack having an enlarged diameter adjacentsaid upper end forming an expansion chamber for diminishing the rate offlow of said gases prior to passing into said outlet.
 10. The structuredefined in claim 9 wherein said container is mounted within saidexpansion chamber.
 11. The structure defined in claim 10 wherein the topof said expansion chamber has a closure, said container being suspendedfrom said closure within said expansion chamber.
 12. The structuredefined in claim 5 wherein said stack has an enlarged diameter adjacentsaid upper end to foRm an expansion chamber for diminishing the rate offlow of said gases prior to passing into said outlet.
 13. The structuredefined in claim 12 wherein said upper end is closed by a closure, saidcontainer being mounted on said closure.
 14. In a cupola having a meltzone adjacent its lower portion for receiving a charge and a stack forhot gases above said melt zone, improved structure which comprises, saidstack having a closed upper end, a container mounted adjacent said upperend and having a body of solid discrete particles contained therein,means operable to introduce particles from said container into saidstack adjacent said upper end in the form of a substantially freelyfalling torrent distributed across a major portion of the diameter ofsaid stack, said stack having an opening in its side above said meltzone, deflector means in said stack effective to deflect said torrent ofparticles toward said opening for discharge from said stack, saiddeflector means also forming shield means effective to shield said meltzone against entry thereinto of said particles in significant quantity,said deflector means having elements spaced apart to define a passagewaywhich facilitates flow of hot gases from said melt zone through saidtorrent toward said upper end, said stack having an outlet for the gasesadjacent said upper end, and a filter connected with said outleteffective to remove particulate matter carried by the gases issuingthrough said outlet, cooling means effective to cool particlesdischarged through said opening, and conveyor means operable to conveythe cooled particles to said container.
 15. In a furnace having a meltzone for metals and a stack for receiving hot gases from said melt zone,improved structure which comprises, a closure adjacent the upper end ofsaid stack, a container mounted adjacent said upper end and having abody of solid discrete particles contained therein, means operable tointroduce particles from said container into said stack adjacent saidupper end in the form of a substantially freely falling torrentdistributed across a major portion of the diameter of said stack, saidstack having an opening below said torrent for egress of said particles,conveyor means operable to return to said container particles which haveissued from said opening whereby to recycle said particles, said stackhaving an outlet for gases adjacent said upper end, said stack having anenlarged portion adjacent said upper end which forms an expansionchamber for diminishing the rate of flow of said gases prior to passinginto said outlet.
 16. The structure defined in claim 15 and including inaddition means effective for cooling said particles between issuancethereof from said opening and recycling thereof.
 17. The structuredefined in claim 15 and including in addition a filter connected withsaid outlet effective to remove particulate matter carried by the basesissuing through said outlet.